Field of the Invention
The invention relates to a device for the transport and deposit of sheets in a stacking region of a rotary press with pneumatic sheet-guiding elements disposed below a sheet-conveying path, said sheet-guiding elements extending across the entire width of each sheet and with a chain-conveyor system, said chain-conveyor system accepting the sheets consecutively from a last sheet-conducting cylinder of the sheet-fed rotary printing press, transporting them along a conveying distance in a main conveying direction directed towards a stack apparatus and releasing them on a stack base in the stack apparatus in order to form a stack.
Such an apparatus is already known from DE 36 29 720 A1, wherein blast-air-activated sheet-guide bars are disposed in the sheet-conveying direction, outer sheet-guide bars each being limited by a suction tube. Starting from the central sheet-guide bar, which distributes blast air on either side, there is formed between the individual sheet-guide bars and the outside-disposed suction tubes a tangentially directed flow field, which stretches the sheets being transported, starting from the centre, transversely with respect to the sheet-conveying direction. Such an arrangement may lead to the setting-off of ink on the upper sections of the sheet-guide bars, particularly in the case of the delivery of face-and-back-printed copies. Furthermore, this solution from the prior art has the disadvantage that gripper bars, carried by revolving gripper chains, are guided over the delivery stack, with the result that, for example, the removal of an inspection sheet represents something of a risk of injury for the printer.
Known from DE 38 41 909 C2 is a process and a device for the floatation-guiding of sheets or web-form material over a conveying distance, particularly a curved conveying distance along one chain side of a chain-conveyor system. Disposed underneath an initially concavely curved and thereafter convexly curved conveying path is a multiplicity of nozzle boxes, separated from each other by suction shafts. Since the partial vacuum acting in the suction shafts replaces the air cushions produced by the open jets escaping from the nozzle boxes, there results a wave-shaped guiding of the material that is to be transported. Provided on the side of the sheets facing away from the nozzle boxes is a plurality of open-jet nozzles, which act from said side on the sheets to be transported. Additionally formed on the conveying chain are blades on which is formed a flow shadow before the sheets enter a duct, formed by a partition wall, with narrowing cross section. Also in this known device, the chain-conveyor system extends over the stack and there are no special measures for the smear-free deposition of the sheets on the stack.
The outlined solutions from the prior art have the common disadvantages that revolving chain systems extend over the stacking region of the sheets, that said chain systems considerably restrict the inspectability of said stacking region and the accessibility thereof and that the removal of an inspection sheet harbours a risk of injury owing to the revolving chain systems.